1. Field of the Invention
The present invention relates to the separation of acetone from methanol and aldehyde impurities by treatment with a basic material and a lower glycol.
2. Description of the Prior Art
Methyl tertiary butyl ether (MTBE) is an important industrial chemical useful, for example, as a fuel additive. In commercial practice, MTBE is produced by the reaction of methanol with isobutylene and/or tertiary butyl alcohol. An important source of the isobutylene and/or tertiary butyl alcohol is from the Oxirane process which is widely practiced commercially for the coproduction of propylene oxide and tertiary butyl alcohol. The isobutylene and/or tertiary butyl alcohol produced from the Oxirane process tends to also contain oxygenated impurities such as acetone and methanol as well as aldehydes.
While the bulk of the acetone can be separated by distillation, the resultant acetone fraction is contaminated with methanol which forms an azeotrope with acetone as well as with close boiling aldehydes such as butyraldehydes with acids such as butyric acid, and with impurities such as methyl ethyl ketone, tertiary butyl alcohol, MTBE and the like which form azeotropes with water.
It has previously been known to separate aldehyde impurities from acetone by treatment with aqueous caustic or with solid caustic. See U.S. Pat. Nos. 2,624,699, 2,906,675, 2,906,676, 3,668,256 and 4,329,510, for example. Such prior techniques are not, however, satisfactorily applied to acetone derived from the Oxirane process. The use of solid caustic causes the formation of excessive heavy material while the use of aqueous caustic results in the introduction of water which cannot be readily removed due to the formation of low boiling azeotropes with various impurities associated with the acetone.
It has been suggested in the prior art that mixtures of methanol and acetone can be separated by extractive distillation using various agents including lower glycols as extractive distillation agents. See U.S. Pat. No. 4,584,063.